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Re: Air Compressor ~ which one to buy?Posted by Rod (NH) on May 13, 2004 at 13:01:02 from (12.148.160.138): In Reply to: Air Compressor ~ which one to buy? posted by Kerry Brunner on May 10, 2004 at 19:39:37: Hi Kerry, Well, since no one else has attempted to answer your questions, I'll give it a shot. You should try to match your compressor capacity to the maximum required capacity of any tools you anticipate using. Compressor capacity is stated as so many cubic feet per minute (cfm) of air delivered. This cfm number is in terms of free air at the compressor intake. It is usually given at one or sometimes two discharge pressures such as 6.5cfm@ 40psig and 5.4cfm@90psig. It is sometimes indicated to be scfm (for standard cubic feet per minute) but that really is a misuse of the term and is not correct for any compressor location other than close to sea level and 60 deg F. Do not go by horsepower of the motor. Today many manufacturers grossly overstate the HP rating to the point of being meaningless. Such overstating is common, unfortunately, in the under $1000 class. There has even been a class-action lawsuit concerning this deceptive practice by even big name manufacturers. You will find that some tools require a lot more air than others. To try and sort out the number games that are played here can be very confusing indeed. Typically spray guns and sanders take a lot. Sandblasting takes an awful lot and you would be disappointed with anything but tiny spot blasting using a $500 compressor. If you can supply a typical full sized spraygun for a reasonable time period w/o the tank pressure dropping below 70-90 psig, you can be assured you can operate most tools although you might not be able to run sanders for long periods without having to stop and wait for the compressor to catch up. Filling tires, cleaning (blowing off), impact wrenches, etc. don't usually take a lot of air, are used on a rather intermittent basis and should not be a problem with any compressor in the price bracket you are talking. Ideally, for a home shop compressor, you should shoot for something like a two stage machine up in the range of 15-20 cfm. You will not find that in the $500 bracket. More like $1500. Usually one has to compromise regarding the ideal :o(. I got along for a number of years with a single stage 6.8cfm@90psig compressor but it was really too small for any serious painting with a full sized gun. I think you ought to be thinking of something like 10cfm minimum at 90psig with as large a storage tank as possible; 60-80 gallons for example. The smaller the compressor capacity, the more important the larger storage is. This is obviously not a portable machine. I don't know if you can find that in the $500 bracket. It should be a lubricated compressor. Most non-lub units will be high speed and obnoxiously noisy. You will also need to think in terms of a 230 volt electrical supply if you don't have one available. All the 110v machines are too small for anything but filling tires and using impact wrenches although they should run a small touch-up spray gun OK. Also, you can pretty much ignore any rating at 40 psig (it will always be greater than the number at 90 psig). Few tools use tank pressures as low as 40 psig so that rating is not particularly important for most shop uses. A two stage machine is always preferable but not likely in the price range you stated. A compressor is a major tool purchase. Unfortunately a first compressor usually winds up to be too small later on, typically because of understandable first cost considerations.
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Rod
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